How old do you have to be to sponsor a child in Africa?

I have been looking all over the internet and I messaged organisations but I can't find anything and no one has answered me yet. Does anyone have any ideas... keeping in mind that sponsoring a child is completely different from adopting one.

Updates:

So to answer my own question age is not relevant you just need a credit card. Luckily my parents support me and allowed me to use their card with obvious expectation that I pay them back. I am very excited.

Charity should begin at home, Africa is a bottomless pit aid wise and it gets enough attention. You could donate to the Nepal earthquake appeal if you really want to do some good abroad, my buddy watched a baby dying in the sun out there last week, their need is probably greater.

If I sponsor this kid it could help their and their siblings go to school, get food, and clean water. It may only be only one little family but it is making a difference. I can sponsor this family for years. I don't know to me that is more rewarding. And just because this kid isn't in Nepal doesn't mean they don't have it bad.

I spent time in Africa back in the day, I don't really want to go into why I feel this way but I assure you it's not based on any prejudice; people should stop giving aid to Africa, it's marketed too damn well.